#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn=2e5+100;
const int mod = 1e9+7;
int a[1005];
int main() {

  int t;
  scanf("%d",&t);
  while(t--){
    ll n,m;
    ll minn=1e18;
    scanf("%lld%lld",&n,&m);
    for(int i=0;i<n;i++){
      ll x,y;
      scanf("%lld%lld",&x,&y);
      ll tmp=m/x;
      if(m%x) tmp++;
      minn=min(minn,tmp*y);
    }
    printf("%lld\n",minn);
  }
  return 0;
}